1. Field of the Invention
The present invention relates to the inspection of mounted components, for inspecting the presence or absence of a component at a prescribed position on a circuit substrate, a deviation from the ideal position of a component mounted on a circuit substrate, whether or not the direction of polarity of a component mounted on a circuit substrate is correct, and so on.
2. Description of the Related Art
Conventionally, the inspection of mounted components is carried out using a template recorded in a component library. Furthermore, one type of the mounted component inspection using a template is an inspection using a master template and a spare template, which is disclosed in Japanese Patent Application Publication No. 2003-110298. In the inspection disclosed in Japanese Patent Application Publication No. 2003-110298, when, for instance, there is low coincidence between a mounted component and the master template, then the template used is switched from the master template to the spare template. By switching between the master and spare templates in this way, the inspection takt time is improved, in other words, the inspection time is shortened.
FIG. 15 shows the composition of a mounted component inspection apparatus disclosed in Japanese Patent Application Publication No. 2003-110298. FIG. 16 is the flowchart of a mounted component inspection method disclosed in Japanese Patent Application Publication No. 2003-110298. Below, the conventional inspection of mounted components as disclosed in Japanese Patent Application Publication No. 2003-110298 will be described with reference to FIG. 15 and FIG. 16.
Firstly, the conventional mounted component inspection apparatus will be described with reference to FIG. 15.
In FIG. 15, a camera 1 captures an image of a substrate 3 mounted on a stage 2. The substrate 3 is a circuit substrate, for example. A component 4 is mounted on the substrate 3. The component 4 is an electronic component, for example. Furthermore, illumination light is irradiated onto the substrate 3 from an illumination unit 5. The image captured by the camera 1 is input to an image processing unit 7 via an imaging unit 6. The imaging unit 6 corrects the brightness of the image captured by the camera 1 and converts the scale of the image from meter units to pixel units.
By processing the image input via the imaging unit 6, the image processing unit 7 performs the inspection of the state of mounting, such as the inspection of whether or not there is a component at a prescribed position on the substrate 3, inspection to confirm whether or not an incorrect component other than a prescribed component has been mounted at a prescribed position on the substrate 3, inspection of the position of the mounted component 4, and inspection of the amount of deviation of the mounted component 4 from an ideal mounting position.
More specifically, the image processing unit 7 comprises: an edge portion extraction unit 8, a template composition/registration unit 9, a matching calculation unit 10, a component position measurement unit 11, a template selection unit 12 and a template use frequency updating/storage processing unit 13.
The edge portion extraction unit 8 extracts the edge portions of electrode portions, which are one portion of the outline of the component under inspection, from the input image. The template composition/registration unit 9 composes a template on the basis of the extracted edge portion, and registers the template thus composed in a component library (not illustrated). The matching calculation unit 10 carries out the inspection of the mounting state described above by implementing a matching process on the input image using the registered template. The position of the mounted component 4 and the amount of positional deviation of the component 4 are determined in pixel units. The component position calculation unit 11 converts the position of the component 4 and the amount of positional deviation of the component 4 which have been determined in pixel units, into dimensions in meter units. The template selection unit 12 switches the template used for the matching process. The template use frequency updating/storage processing unit 13 updates the frequency of use of the template, and stores the frequency of use after updating in the component library (not illustrated).
Next, the conventional mounted component inspection method will be described with reference to FIG. 16.
Firstly, at step S1, images of components of manufacturers which are the objects of inspection are captured by the camera 1, and the edge portions of the electrode portions of the components are extracted by the edge portion extraction unit 8. More specifically, the edge portions of the electrode portions apart from the boundary lines between the main portion and the electrode portions of the component are extracted.
Next, at step S2, the template composition/registration unit 9 composes and registers templates for the respective components on the basis of the edge portions thus extracted.
Thereupon, at step S3, the template selection unit 12 selects, from component-specific templates of components which are expected to be mounted, the template with the highest recent use frequency, in other words, the template of the component having the highest probability of being mounted.
Thereupon, at step S4, the matching calculation unit 10 performs the above-described inspection of the mounting state by using the selected template. At this point, if the evaluation value of the matching process such as the degree of coincidence in matching, is lower than a reference value, then the procedure returns to step S3, and the template selection unit 12 automatically switches the template to be used to the template having the next highest frequency of use, and carries out the inspection of the mounting state at step S4, once again. In this way, the template selection unit 12 switches the template to be used to a template having an evaluation value higher than the reference value.
Next, at step S5, the template use frequency updating/storage processing unit 13 updates the frequency of use of the template which has ultimately been used in the matching process.
Thereupon, at step S6, the component position calculation unit 11 calculates, in meter units, the position of the component 4 and the amount of positional deviation of the component 4, which have been determined in pixel units.
From step S6 onwards, the steps S3 to S6 described above are repeated until the completion of the inspection of the whole inspection area where the inspection of the substrate 3 is required.
In this way, in the conventional inspection of mounted components, a template having a high frequency of use is used preferentially. Therefore, the number of switches of the template is reduced statistically, and the time required for the matching process can be shortened. Consequently, the inspection takt time is improved, in other words, the inspection time is shortened.
As described above, in the conventional mounted component inspection, the template used is switched to the template having an actual evaluation value higher than the reference value. However, in this conventional mounted component inspection, if the recognition rate does not improve even when the templates are switched, then even supposing that the component library is adjusted to include template changes, it is not possible to ensure that the component library after this adjustment represents an improvement compared to the component library before adjustment. Here, the recognition rate means the rate of the number of times that correct recognition is made with respect to the number of times that the inspection is performed. Furthermore, false recognition means that correct recognition cannot be performed.
In particular, in a production line in which 1000 or more components are mounted on a single substrate, many components of different types need to be inspected and therefore, a recognition rate of the level of several PPM (parts per million), more specifically, an allowable rate of several false recognitions per million times is required. In a production line of this kind, when the component library is adjusted, any new problems caused by such adjustment do not become apparent simply by confirming whether or not recognition is performed correctly in several substrates immediately after the adjustment of the component library, but rather the satisfactory or unsatisfactory nature of the recognition rate is revealed later on, after the adjusted component library has been introduced. When the poor recognition rate becomes apparent, the adjusted component library has to be adjusted again at that point and returned to the original component library.
In this way, in the conventional mounted component inspection, since there is no means of confirming quantitatively that an improvement in the performance of the component library has been achieved by adjustment, then it has taken time until the level of this performance can be assessed, and therefore it has required time to re-adjust the component library. Moreover, since it takes time until the satisfactory or unsatisfactory nature of the recognition rate is revealed, then unless similarities and differences between the component library before adjustment and the component library after adjustment are managed suitably, the time taken to re-adjust the library in order to return to the original component library progressively increases.
These problems are especially pronounced in cases where many different types of components are mounted, and where there is a plurality of component libraries requiring adjustment. Furthermore, in this case, in the conventional mounted component inspection, since there is no means of confirming the improvement made in the performance of the component library through adjustment quantitatively, then it has been difficult to specify which component library should be adjusted. Furthermore, if there are many different types of components to be mounted, then the management of recording of differences between the component libraries before adjustment and the component libraries after adjustment is complicated, and this places an increased load on the operator.
As described above, in the conventional mounted component inspection, it has not been possible to re-adjust the component libraries quickly.
Furthermore, in the mounted component inspection, the shape of the object under inspection is not uniform, but rather includes a plurality of shapes. Therefore, creating and improving the component libraries, which is a key requirement for the inspection, need a high level of expertise. However, recently, specialist operators having sufficient expertise are not necessarily present in component mounting sites, and therefore it is necessary to improve the performance of the component libraries in consideration of this situation in the field.